Grounding Floor Glide for Shelving, Chairs, and Equipment to Reduce Risk from ESD (Electro-Static Discharge) and Protect Floors from Damage

ABSTRACT

This conductive ESD protective foot is a grounding device consisting of a resilient conductive floor glide (foot) that provides an electrical path from a shelving unit, chair, or other equipment, to a conductive floor. The foot can be installed onto a leg leveling bolt or, alternatively, inserted into the shelf post itself. This foot provides an electrical connection for ESD purposes while it allows a device using this foot to be moved without causing damage to the floor. This device provides a conductive path to the floor, allows a shelving unit to slide more easily across a floor without damage and separates metal leg levelers (bolts) from the floor, which reduces risk from rust stains caused my metal legs rusting to the floor from use of water or cleaning methods 
     This Foot protective foot can be installed and removed without the use of tools and is held securely in place when attached. It allows for some variation in bolt-head size as well as post inside diameter, which increases its flexibility, as the Heavy-Hex bolts used as leg levelers have bolt-heads that often vary depending upon the manufacturer. If an electrically conductive version is not required, non-conductive material can be substituted to reduce cost.

CROSS-REFERENCE TO RELATED APPLICATIONS

None.

SEQUENCE LISTING

None.

FIELD OF THE INVENTION

This invention relates to electrostatic discharge (ESD) and in particular, the grounding of shelving, chairs, and equipment to conductive floors while protecting the appearance of floors from scratches and rust stains caused by leveling legs and posts.

DESCRIPTION OF THE PRIOR ART

Conventional shelving units typically include a plurality of vertically standing support posts and at least one shelf horizontally supported by the posts. For example, U.S. Pat. No. 3,523,508, issued to Maslow 1972, and U.S. Pat. No. 3,757,705, issued to Maslow 1970, disclose a shelving unit formed from four support posts, and one or more horizontal shelves provided with a frustro-conically shaped collar at each corner for receiving one of the support posts. A split sleeve is secured to each support post and fits into the frustro-conically shaped collar at each corner of the shelf. The positions of the split sleeves on the support posts are vertically adjustable so the height and relative spacing of the horizontal shelves can be chosen when assembling the shelving structure. These adjustable shelving structures are sold and marketed under the trademark SUPER ERECTA SHELF by InterMetro Industries Corporation, of Wilkes-Barre, Pa. Other similar adjustable shelving structures are offered under brand names such as Eagle and others.

FIG. 1 shows a conventional adjustable shelving unit of the type disclosed in U.S. Pat. No. 3,757,705.

Each post 1 is typically configured with a leveling leg 3 at the base 1-B of the post 1, but, in the absence of a leveling leg 3, the post 1 is sometimes placed directly on a floor, with surface 1-B contacting the floor. The leveling legs 3 typically consist of a galvanized or chrome plated heavy-hex bolt. The height of each of leg leveler 3 can be adjusted to various heights by means of the distance the leg leveler is threaded into the threaded adaptor 2. Although the diameter and thread pitch is consistent, the head size of the heavy-hex bolt 3 varies depending upon the manufacturer.

FIG. 2 shows that a leveling leg 3 (typically a Heavy-Hex bolt) is installed into the post 1 by means of a threaded adaptor 2 which is pressed into the post 1. The leveling leg 3 is prone to oxidation from water or floor cleaning solutions used on the floor and often create rust marks on the floor that are difficult to remove. The sharp edges and corners of the leveling leg's 3 hex head 3 can gouge and scratch the floor if the shelving is slid on the floor.

FIG. 3 shows a post 1 only, where the post base 1-B would be the surface that supports the post 1. Since the post 1 is typically made from ferrous metal, the base surface 1-B often leaves rust rings that become embedded into the floor if the shelving is stationary for a period of time or will scratch the floor if the shelving is slid a new position.

FIG. 4 is a common example of leveling leg 5 with an insulative plastic insert 7, typically nylon, that is used to protect floors. Although it may protect a floor from scratching, it does not provide an electrical connection between the shelving unit and a conductive floor, and it requires a threaded insert 2, so it cannot be inserted directly into a post 1

FIG. 5 shows a leg leveler 8 with an insulative head 9 molded onto a leg leveler 8. Similar to the item if FIG. 4, it may protect a floor but does not provide an electrical connection between the shelving unit and a conductive floor, and also requires a threaded insert 2, so it cannot be inserted directly into a post 1.

FIG. 6—FIG. 8 shows a common insulative soft rubber foot 4 that is commonly used to protect floors from damage from leveling legs 3. This type of rubber foot 4 fits one size of Heavy-Hex bolt head only, whereas the size of heavy-hex bolts that are provided with shelving varies depending upon the manufacturer, so this type of rubber foot 4 can only be used with one specific size of heavy hex bolt. This floor protector is soft, and therefore does not allow a shelving unit to easily slide across the floor. Additionally, the rubber foot 4 eventually sticks to the floor and is insulative, so to ground the shelving requires the addition of a separate grounding wire from the shelving to a common ground. If the shelving unit is not near a ground, it can be challenging to ground the shelving with this type of insulative rubber foot.

BACKGROUND

Static electricity is commonly defined as an electrical charge resulting from the imbalance of electrons on the surface of a material. Most people are quite familiar with the everyday effects of static electricity—it is the shock one receives when touching a doorknob after walking across a carpet. The technical name for the electrical shock just described is electrostatic discharge (ESD). ESD is technically described as the transfer of electrical charge between bodies—for instance, a human hand and a doorknob—that are at different electrical potentials.

In most everyday situations, ESD can be a bother but rarely a problem. However, the problems resulting from ESD are magnified in industrial settings, where ESD is a major concern. Among the many problems that static discharge can cause are the unintentional ignition of flammable materials, damage to electronic components and systems, and the attraction of contaminants such as charged dust particles in clean room environments. Even centuries ago military forces were aware that ESD could cause the unintentional ignition of black powder. To alleviate this sometimes-catastrophic problem, ESD control measures were used as early as the 14th century to protect black powder stores. Today, many industries—from high tech manufacturing plants to businesses commonly thought of as “smoke stack” industries—are concerned with ESD and its control, since controlling ESD can lead to a safer work environment and reduction or elimination of damage resulting from ESD.

While nearly all industries are or should be concerned with controlling ESD, the concern is most acutely felt by businesses in the electronics industry.

To give just a few examples of the damage that ESD can cause in the electronics industry, it can destroy or degrade semiconductor devices by changing operational characteristics. It can cause disruptions to the normal operation of an electronic system—sometimes leading to equipment failure, and in clean rooms it can cause charged particles to adhere tightly to the surface of a silicon wafer, resulting in distinct problems with wafer production and efficiency.

Given these problems and the economic damage that can result from them, control of ESD is a major concern and a complete industry has grown up around the field of ESD control.

Some very common ESD protective measures are to use conductive floors, benches, containers, storage shelves, and transport carts and then connect each of these, as well as products and people, to a common electrical ground. Connecting them to a common electrical ground reduces any build-up of electrical potential between objects, thereby reducing the risk of an ESD event.

A critical component of an ESD control program is dissipating and neutralizing ESD during handling, transporting and storing of ESD sensitive materials.

A common type of shelving unit and transport cart used in the electronics and other industries is a type of wire shelving shown in FIG. 1 through FIG. 3 and discussed in the Description of Prior Art. One reason for its popularity is that both the shelves and posts are metal, and therefore conductive, allowing them to be electrically connected, providing a means to connect the shelving and therefore the material stored on the shelves to a common ground.

Shelving units such as those in FIG. 1 through FIG. 3 (hereafter referred to as shelving units) are typically resting on stainless, galvanized, or chrome leveling legs, or simply resting on the posts themselves.

SUMMARY

Floors in many electronics manufacturing facilities are typically a special electrically conductive vinyl tile, conductive epoxy, conductive urethane, or other appropriate material. A majority of these floors that are white or light gray and are not only functional, but also provide a clean and professional appearance.

Sliding a shelving unit across a floor typically causes floor damage due to the leg leveler bolt-head or the end of a post digging into the floor. The heavy hex bolts used as leg levelers and the posts themselves rust due to floor cleaning solutions and leave rust stains on the floor. Various floor protectors (floor slides) are available, but they are typically made from insulative material, and there are no electrically conductive floor slides that can be installed both on the leg levelers (see FIG. 9-FIG. 14) as well as directly inside the post (see FIG. 15-FIG. 17). The present invention is intended for shelving but also applies to chairs, benches, equipment, and the like. If electrical conductivity is not required, less expensive static-dissipative or insulative material can be substituted. There is a real need for an easier method of providing ESD safe shelving units or furniture while protecting the condition and appearance of ESD floors.

The present invention is an electrically conductive leg leveler (foot) 10 that easily installs onto a leveling leg 3 of a shelving unit, chair, or equipment, as shown in FIG. 12 to FIG. 14 or directly into a shelving unit post 1 as shown in FIG. 15 to FIG. 17. It provides electrical connection between the post 1 and a conductive floor. Additionally, this device provides a non-ferrous surface that will not rust and can slide across a floor without causing damage to the floor.

Objects and Advantages:

Besides the objects and advantages of the electrically conductive foot 10 described in the above patent, several objects and advantages of the present invention are:

-   -   (a) Easy to install onto existing leg levelers 3     -   (b) Can be Installed by inserting directly into posts without         leg levelers     -   (c) Installs onto leg leveler bolt-head of various sizes due to         the friction-fit and lead-in of surfaces 10-A and 10-C, and         corner relief 10-B     -   (d) Installs on leveling legs for chairs and other various         furniture     -   (e) Effective on other types of surfaces besides conductive         floors     -   (f) Reduces damage caused by metal leg levelers or posts rusting         to floor     -   (g) Provides a conductive path for electrical ground to a         conductive floor for ESD purposes     -   (h) Allows the shelving unit to slide across the floor without         causing damage     -   (i) Leveler 3 can be adjusted with a wrench using the hex         surfaces 10D on the outside of foot 10     -   (j) Will not stick to the floor or stain the floor like rubber         feet

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a conventional adjustable shelving unit FIG. 2 is a partial perspective of an exploded view showing one corner of the conventional shelving unit of FIG. 1

FIG. 3 is a partial perspective view showing one corner post 1 of a conventional shelving unit of FIG. 1 without leg levelers 3 and without threaded insert 2

FIG. 4 is a type of leg leveler 5 that includes a plastic insert 7 in the base 6 to protect the leg leveler 5 from scratching the floor

FIG. 5 is a type of leg leveler 8 with an integrated plastic disc 9 as the base

FIG. 6 shows a perspective view of an insulative rubber protective foot 4 that attaches to a the head of a leg leveler 3 as shown in FIG. 2

FIG. 7 shows a Top view of an insulative rubber protective foot 4 that attaches to a leg leveler as shown in FIG. 2

FIG. 8 shows a partially exploded perspective view of an insulative rubber protective foot 4 attached to a leg leveler 3 that is attached to an assembly of a post 1 and threaded Insert 2

FIG. 9 is top view of the present invention

FIG. 10 is a front view of the present invention

FIG. 11 is a perspective view of the present invention

FIG. 12 is an exploded perspective view of the present invention 10 with a leveling leg 3, post 1, and threaded insert 2

FIG. 13 is a partially exploded perspective view of the present invention 10 with a leveling leg 3

FIG. 14 is a top view of the present invention installed on a leveling leg 3

FIG. 15 is an exploded perspective view of the present invention 10 mounted inside of the post 1

FIG. 16 is a partially exploded view of the present invention 10 mounted inside of the post 1

FIG. 17 is a front view of the present invention 10 fully mounted inside of the post 1

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment of ESD protective foot 10 is shown in FIGS. 9 through 17. Foot 10 includes a main body with an internal modified hex-shaped cavity 10-F that accepts a hex bolt used as a leveling leg 3, and an external rounded-off hex shape that is a friction-fit into a round tube, such as post 1 and a resting surface 10-E that supports post 1 when inserted into said post 1 as shown in FIG. 15-FIG. 17.

Foot 10 is made of any sufficiently strong, electrically conductive, resilient, corrosion resistant, and flexible material such as a conductive plastic, conductive rubber, stainless steel, or other similar material.

Foot 10 is typically installed in one of two configurations. The first configuration is the external position, as shown in FIG. 9 through FIG. 14, where foot 10 is pressed onto a leveling bolt 3 where leveling bolt 3 is fully inserted into cavity 10-F as shown in FIG. 13. Tapered surfaces 10-A provide a lead-in for leveling bolt 3 and apply pressure on the flat surfaces 3-A of the leveling bolt 3 and provide a friction fit to retain foot 10 on leveling bolt 3 if leveling bolt 3 is raised off of the floor.

Allowance for variation the head size of the Heavy-Hex bolt used as a leveling leg 3 is provided by two features. The first feature is pressure on flat surfaces 3-A of the hex bolt are held in place by foot inside contact points 10-A The second feature that allows size variation is the hex bolt corner relief 10-B, which accommodates variation of hex bolt 3 points 3-B and.

FIG. 15-FIG. 17 demonstrate the second configuration of installing foot 10 which is to insert foot 10 directly into post 1. Rounded-off hex points 10-C are tapered to provide a friction fit into the inside surface of post 1 and to allow variation in the inner diameter of a post 1. When foot 10 is fully inserted into post 1, post bottom surface 1B will be touching foot surface 10-E as shown in FIG. 13. Post 1 will then be supported by foot surface 10-E and the friction fit inside of post 1 will keep the foot 10 secure inside of post 1. 

1. A rust-proof floor glide providing a means of electrical interconnection between a shelving post leveling leg and a conductive floor that can be installed by installing onto the leg leveler or by directly inserting said floor glide directly the into post consisting of: a. An electrically conductive glide b. Optionally can be constructed with insulative material c. A means of urging said electrically conductive glide against said leveling leg bolt of various size head dimension d. A means of retaining the electrically conductive floor glide of said shelving unit leveling leg of various size head dimension e. A means of urging the electrically conductive floor glide against said post f. A means of retaining the electrically conductive floor glide inside of said shelving unit post g. Optionally may be fitted to other items such as chair legs 